Alkylation of isoparaffinic hydrocarbons



Patented Aug. 20, 1946 ALKYLATION F ISOPAR'AFFIhTIC 7 Carl B.'.Linn,

Oil Products Company,

j tion of Delaware I No Drawing. Application September Serial No. 502,664

7 Claims; (Cl. 260-6834) v 1 This application is a continuation-in-part of my co-p'ending application Serial No. 424,784,

' filed December 29, 1941.

This invention relatesto the'treat'ment of isoparaflinic hydrocarbons, both gaseou and liquid,

to produce therefrom branched chain parafiinic hydrocarbons of higher molecular weight. In a more specific sense this invention is concerned with a novel process for alkylating isoparafiinic hydrocarbons, comprising isobutane and relatively low-boiling normally liquid isoparafiins with normally gaseous or liquid olefins to produce normally liquid saturated hydrocarbons which may be utilized as components of gasoline suitable for use in airplane and automobile engines.

These isoparaflinic and olefinic hydrocarbons have been utilized in alkylation reactions in the presence of hydrogen fluoride alone or of hydrogen fluoride diluted by-relatively small quantities of water. The present type of catalyst is a marked improvement over previous catalysts con- -taining hydrogen fluoride in that the activity of the catalytic material may be controlled more accurately by proper dilution with a substance which is relatively inert catalytically but which has substantial solubility in-liquid hydrogen fluoride.

In one specific embodiment the present invention comprises a process for synthesizing substantially saturated hydrocarbons of gasoline boiling range by alkylating isoparafiinic hydrocarbons with olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of a liquid hydrogen fluoride and a relatively minor proportion of hydrogen cyanide.

By the addition of hydrogen cyanide to sub stantially anhydrous hydrogen fluoride, the ordinarily vigorous reaction of hydrogen fluoride on catalytic condensation reactions among hydrocarbons is moderated to the extent that reactions of alkylation occur in preference to other -'less desirable reactions. Alkylation is essentially a complex reaction since the simple union :of isoparafiinic and olefinic molecules to give the sa-called primary reaction product is accompanied by many side reactions, among which are decomposition or cracking reactions and isomeritzation, which can, under certain conditions, achange a substantial proportion of the primary 1 product such as iso-octanes into a mixture of lower? and higher boiling hydrocarbons fre. 'quently-of; lower antiknock value. Accordingly, the present invention deals with the modification HYDROOARBQN S Riverside, 111., assignor to Universal Chicago,.1ll., a corporaof hydrogen fluoride alkylation catalyst by the addition thereto of a particular non-oxidizing acid which moderates the action of hydrogen fluoride and modifies the reactions involved in such: away as to improve the yieldand quality of the hydrocarbon alkylation product. The term isoparafiln is herein used broadly .to include all alkylatable branched chain parafiinic hydrocarbons. The reactions of the present process are effected under controlled conditions of temperature and pressure until the olefin have been substantially consumed and asubstantially saturated hydrocarbon product is formed which boils within the boiling range of gasoline.

Hydrogen cyanide i a Weak volatile acid and like hydrogen fluoride it is a liquid at ordinary temperatures and atmospheric or slightly superatmospheric pressures. Hydrogen cyanide has a boiling point of 26.5 C. and hydrogen fluoride boils at'19.4C. The melting points of hydro.- gen cyanide and hydrogen fluoride are 1'3.4 C. andf-92.3 0., respectively. Hydrogen cyaniche is "soluble in water, alcohol, andether, and also in hydrogen fluoride in the concentrations which are contemplated in the presentprocm. Ordinarily the catalyst employed in my invention may comprise from about O.5-to about 10% by weight of hydrogen cyanide although larger quantities may be used in certain cases. Because of its toxicity and attendant difiiculties when employed in high concentrations it is generally desirable to maintain the hydrogen cyanide content of the catalyst below about 5% by weight.

Isobutane is the isoparaflin commonly subjected to alkylation although higher molecular Weight isoparafiins also react with olefins under similar or modified conditions of produce branched chain parafiins of higher boiling point than the isoparafiins charged to the process. However, as the higher 'molecular weight isoparaflins such as isopentane, isohexane, etc. are themselves Valuable constituents of gasoline, they are consequently used less commonly as charging stocks for the alkylation process than is isobutane. Mono-olefin and particularly those containing from 3 to about 16 carbon atoms per molecule are utilizable for alkylating isoparafilns in the presence'ofhydrogen fluoride and a diluen't'or spacing agent, although the common olefin-containing charging stocks are often limited to hydrocarbon fractions containing ethylene; propene, and butenes. Normal parafiins frequently present in hydrocarbon fracreacting hydrocarbons but are separable operation to as isobutane, which is f proximately 5:1.

upper limits of .diluents for use with; hydrogen jalkylation products by distillation. Thus profpane and normal butane may be removed from the alkylation product while an isoparafiin such also separated from the reactionproduct, is recycled to further alkylation treatmentj.

In order "to f avor the alkylation reaction rather polymerization,

containing mixture charged.

Alkylation reaction about 0 and about 50 C. are preferred, although satisfactory results {maybe obtained at temperaturesaslow as about -30 and as high as about +100? 0. when reacting isoparaffins with olefins in the presence of a mixturesof hydrogen fluoride and a diluent or spacing agent .asherein *described. As additional means of regulation of the temperature, ther-proportionsyo-f hydrogen fluoride and diluentmay be'varied; to .produce good results :provided they are co-ordi- -natedproperly with the reaction temperature and rate of charge of theisoparaffin and olefin hydrocarbons. Forinstance, the reaction of isobutane with propene may require moresevere conditions such as a somewhathigher temperature or a cat- -alyst containing-a higher proportion'oi hydrogen fluoride. todiluent thanthat used for catalyzing .the reaction of isobutanewith the more reactive isobutene. *Superatmospheric pressure; generally :not in excess of about 20. atmospheres, is employed to assist the reactioniandto *preventundue "loss 'of'the reactants and catalyst lay-vaporization and, when desirable, to maintainthe hydrocarbons nd ca alyst in substant ally l u dmsta r o effect liquefaction of alportion of the'reaction mixture.. j

W hile in most cases the actiyity' oif. the alk ylatin composite employed-is due principally -to the dr enrfi ori ait is reco ized't tthe ydrogen cyanide added theretomay at times; exert a definite chemical influence upon therreactions other than merely moderating the BfiBQtaDf'tHG hydro en uo de.- It s als e dent thatzthe selection of any particula diluentcrap xtureof V flu ide; s--'determined largely'by solubility relations; the; ease of alkylating the; isoparaffinlc hydrocarbonsinvolyed, the general operating conditions, and the matter of economy-in the cost'of. the reagents,

' The process of the present-invention is carried outin either batch or continuous types oto-peration. In a simple batch. tyne pro ess. an-;-iso.- parafiin to be. alkylated suchas isobntane, is brought to the alkylating temperature withinithe approximate range specified and in the; presence .of the necessary amount of catalyst mixture and alkylation iseffected by the gradual introduction of an olefin, or preferably of an olefin-isoparafli mixture, underthe surface of the liquid lwhich is stir-red mechanicallyto effiect intimate contact between the catalyst and the; reacting drocarbons and; to prevent settling ofgthe -catalyst .which is heavier than the liquidtihydrocarbon mixture. to different stages of reaction, In-the case ofithe :;.a y1 tion of s ne by propane: or butenes.--

Alkylationamay be-'allowed-toprogress the hydrocarbon charging stock includin the isoparaflin and"! added olefin-containing fraction may be com.- mingled with recycled isoparaffin so thatthejratio 1 of isoparafiin to olefin in the total hydrocarbon 1 mixture charged to the alkylation zonenis zap-,1

In some ca'ses- 'this ratio may i be as low as about 2:1 or as high as :1, or more, i 1 the exact'ratio being somewhathependentupon. the particular isoparaffin and'blfin or olefin! 4 ess. The'exce'ss' temperatures between 1 and separated into catalyst layer, the reaction zone :for further bonlirlayertx' bends o hrunonalk-ylation Y reactor quite: often; of a; coil or tower provided with baiiies, orifice plat s,.ao the mixin ;d vicesioria-vess l provided with a stirrer orother mechanical means -mately sure-sealed stirring device; 'maintained: at approximately 50 of a liquid. mixture containing:2 molecular proportions? of isobutane and 1t moleculan-proportion of normalbutene is 1 introduced: continuously:-: to

good products from the standpoint of high antiknock gasoline are produced usually by maintaining at alltimes in the reaction zone a molar excess of isoparaffin to olefin. The presence of such an excess of isoparafiins, generally at least 2lmo1ecular proportions ofisoparaifin per molecularcproportiont of olefin,tends to minimize undesirable polymerization reactions. The mixture of alkylation products and catalyst composite is removedperiodically from thebatch type process a hydrocarbon layer and a latter being returned, to the use while the hydrocar- '.;fractionally distilled to separate therefrom the gasoline fraction and the excess 10f the isoparafiinloriginally charged to the procbasis by: withdrawparaflins, an alkylate of. gasoline boiling :range, higher boiling hydrocarbons; and. catalyst-composite, said -mixture being withdrawn atzsubstantially the. same rate-as thatat whichthe -tresh and recycled hydrocarbon charging stocls and mixture of fresh and recycledcatalyst are supplied to the alkgylation-reactor. In iorder to-zkeep low the competing olef n :polymerizationreaction, the molar ratio of isoparaffins.to-plefinsiQZ-the alkylating zone. is"kepthighithroughoutthe entire reaction; The ratio of. isoparaff n-toolefin issubjectto some variation and is affected considerably by the method of introducing the olefincontaining fraction andby th efliciency; oimixing. =As theiprocess-is' usually operated; sulii-cient pressure is=maintained1 'upon'. thereaction turev to eep: a substantial; proportion ther'eo f n liquidstate. The exactv pressure necessary ;de-

the ompo it on o-fg he reaction mixture-and the temperature employed. The se i ti "p Qess'..-c0 SiSl of agitation although any method may here nployed' which; satisfactorilyeffects {intimate con- -tact of the reactinghydrocarbons:and-mixture uoiicatalyst-and. spacing-r agent employed; 7

The following'exampl e isgiven toindicate'f 11 6- sults obtainablerby the ;use of theipresentrprocess, although :ity is not intended to: limit the seopezof the inventionw-in exact correspondence;-;with the example. V,

A mixture of 143 grams of substantiallyoarrhydrous hydrogen fluqrideandflgramsof'hydrogen v cyanide is; placed inan autoclave ofriapproxir 2000 a-cc. capacity equipped --witht a ipresiThe autoclave-11s the autoclaveover:afperiod -or li5jhourssafter i which the stirring [is continuedforran: additional time-of 0;5 hour.V i

The, r nt: mixture. ofreactionproducts; is separated into a hydrocarbonilayer an'd a heavier ca yst Jaye-r. The :used: catalyst :is'returnedcito the autoclave for use. in. another alkylatiomrun while the; hydrocarbon layer. is jractionallm'distilled: to separate: from: higher boiling; alkylation products the 'unreacted' isobutane anduz small isoparaflin may be reacted further with an olefin in a subsequent alkylation treatment'in the alkylation zone of the process.

It is usually preferable to carry out the alkyla =tion; reaction on a continuous ing fromthe alkylationreactor amixtureof excess unreacted isoparafiins; and: admixedenormal' presence of a liquid which has been hydrogen cyanide.

amounts of hydrogen fluoride which generally dissolve in the hydrocarbon layer. The recovered isobutane is used in another alkylation run while the higher boiling hydrocarbons are washed with water and caustic soda solution, then dried and distilled to separate therefrom a substantially saturated fraction of gasoline boiling range containing a high proportion of branched chain octanes.

From 1000 cc. of the isobutane-norm'al butene mixture there is obtained approximately 3'70 grams of normally liquid paraffinic hydrocarbons containing 90% by volume of 300 F. end point aviation gasoline with an A. S. T. M. octane number of 92.5.

I claim as my invention:

1. An alkylation process which comprises reacting an isoparafiin with an olefin in the hydrogen fluoride catalyst to added a minor proportion of 2. A process for synthesizing substantially saturated hydrocarbons of gasoline boiling range which comprises alkylating an isoparafiinic hydrocarbon With an olefinic hydrocarbon in the presence of a catalyst consisting of a major proportion of liquid hydrogen fluoride and a minor proportion of hydrogen cyanide. I

3. The process of claim 1 wherein said hydrogen cyanide comprises from about 0.5 to about by Weight of the catalyst.

4. An alkylation process which comprises concyanide.

6 Y tacting an isoparaflinic hydrocarbon With an olefinic hydrocarbon at a temperature of from about 30 C. to about catalyst comprising essentially a major proportion of liquid hydrogen minor proportion of hydrogen cyanide.

5. An alkylation process which comprises contacting an isoparafiinic hydrocarbon with an olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion of hydrogen cyanid at a temperature of from about -30 C. to about 100 C. and under sufficient pressure to maintain a substantial proportion of the reacting hydrocarbons and catalyst in the liquid state.

6. An alkylation process which comprises contacting a molar excess of an isoparatfinic hydrocarbon with an olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion of hydrogen cyanide at a temperature of from about 30 C. to about 100 a substantial portion of the reacting hydrocan bons and catalyst in the liquid phase.

7. An alkylation process which comprises reacting isobutane with a mono-olefin in the presence of a liquid hydrogen fluoride catalyst containing a minor proportion of hydrogen CARL B. LINN.

C. in the presence of a fluoride and a relatively C. and under sufficient pressure to maintain 

